Hydraulic punch and stripper



Dec. 19, 1950 o. MuELLr-:R

HYDRAULIC PUNCH AND STRIPPER 8 Sheets-Sheet l Filed Jan. 18, 1947 mmw@ Otto fz/eZer v BY u /77H ORA/EVS 0- MUELLER NCH AND STRPPER Dec. 19, 1950 HYDRAULIC PU INVENTOR,

Offb MVC [le r' ww) f O. MUELLER HYDRAULIC PUNCH AND STRIPPER Dec. 19, 1950 8 Sheets-Sheet 5 Filed Jan. 18, 1947 l IN VEN TOR. Otto M-z/eer' x BY HTTORA/EKS Dec. 19, 1950 o. Mur-:LLER

HYDRAULIC PUNCH AND STRIPPER 8 Sheets-Sheet 4 Filed Jan, 18, 1947 umn f77" TURN/vrs.

Dec. 19, 1950 o. Mur-:LLER

HYDRAULIC PUNCH AND STRIPPER Filed Jan. 18, 1947 8 Sheets-Sheet 5 INVENTOR. Offo M-z/eZer.

BY M' Dec. 19, 1950 o MUELLER HYDRAULIC PUNCH AND STRIPPER 8 Sheets-Sheet 6 Filed Jan. 18, 1947 Offo Mue'ef Dec. 19, 1950 o. MUELLER 2,534,292

HYDRAULIC PUNCH AND STRIPPER Filed Jan. 18, 1947' a sheets-sheet 7 NMMIH ullm Sw gm Mw www \,WM m .l N Y *wi A Aw 4 @mi www .m Emi 1 .34.- 1 wwnmwww LILI ii Dec. 19, 1950 o. MUELLER 2,534,292

HYDRAULIC PUNCH AND STRIPPER 8 Sheets-Sheet 8 Filed Jan. 18, 1947 22414 f4.4 r" 0 ne lNvgNrolz. O f fo we cr Patented Dec. 19, 195t'! Y UNITED STATES PATENT OFFICE HYDRAULIC PUNCH ANDl s'ralrrnn c om Mueller, Dearborn, Mich. Application January 1s, 1947, serial No. '122,935

27 claims. (c1. 164-95) The present invention relates to hydraulic punching and stripping devices, and more particularly relates to a unit 'device foroperating metal working tools and a pressure plate for holding andstripping the material from the tool, and generally constitutes an improvement over the structuredisclosed in United States Letters understanding@ the invention, to the following Patent 2,353,488, issued July 11, 1944, for Hyon a base or table or incorporated in a press or die unit for punching holes in sheets of metal.

Another object of the present invention is to provide a punch and stripper mechanism in which a piston, movable in a xed cylinder, drives a tool supporting head carrying a punch and pressure plate, which plate is operable by an auxiliary piston in the tool supporting head to clamp a piece of work while the same is punched and the punch stripped therefrom.

Another object of the present invention consists in the provision of a punch and stripper including a compound cylinder movable on a. xed piston, having an auxiliary piston thereon movable with and independently of said compound cylinder, and carrying a punch and a pressure plate, which plate is operable by the auxiliary piston to clamp a piece of work while the punch is forced through and stripped from the work.

A further object of the present invention is to provide a punch and stripper unit of the type described which is carried on a resiliently restrained member actuated by a piston in the unit' to bring a punch and pressure plate into operative engagement with a piece of work in cooperation with a second punch and pressure plate which is also actuated into operative engagement with the work by the piston.

The invention further contemplates apparatus of the type mentioned for punching holes in the opposed sides of channel members or other similarly shaped metal structures through use of opposed punching4 means.

Still further, the present invention contemplates apparatus of the type descrbedfor punching holes in opposedsides of channel members in which a single punch member is adapted to penetrate opposed sides or walls of a piece of work.

Other objects and features of novelty of this invention will be specifically pointed out or will become apparent when referring, for a better companying drawings, wherein:

Figure 1 is a plan view of the punching device embodying the improvements of the present in- Vention;`

Fig. 2 is a sectional view of the structure i1- lustrated in Fig. 1, taken on the line 2--2 there- Fig. 3 is a View of structure, similarto that illustrated in Fig. 2, showing .the punch in retracted position;`

Fig. 4 is a sectional view through the ram structure, taken on the line 4:4 of Figure 2;

Fig. 5 is a sectional view of the structure i1- lustrated in Fig. 2, taken on the line 5 5 thereof;

Fig. 6 is a broken sectional 4View of structure embodying a further improvement of the present invention;

Fig. 7 is a sectional view of the structure illustrated in Fig. 6,- taken on the line 1-1 thereof;

Fig. 8 is a plan view of a further form of the present invention;

Fig. 9 is a sectional view of the structure illustrated in Fig. 8, taken on the line'S-Q thereof;

Fig. 10 is a broken sectional view ofthe structure illustrated in Fig. 9, taken on the line I--Ill Fig. 11 is a sectional view of still another form of the present invention;

Fig. 12 is a sectional view of the structure shown in Fig. 11, taken on the line |2-l 2 thereof;

Fig. 13 is a sectional view of structure illustrating a further form of the invention;

Fig. 14 is a sectional view of the structure i1- lustrated in Fig. 13, taken on the line |4-l4 thereof;

Fig. 15 vis a plan view, partly in section, of` a further form of the invention, having the structure illustrated in Fig. 13 embodied therein;

Fig. 16 is a sectional View of the structure i1- lustrated in Fig. 15, taken on the .line IS-IS thereof;

Fig. 17 is a sectional view of the structure illustrated in Fig. 16, taken on the line I'l-Il may be assembled ln gangs for punching holes in work of considerable length. For the purpose of simplification in the description, only one punch of lthe unit is described. However, it is not intended to limit the invention thereby.

Referring to Figs. 1 to 5, inclusive, one form of the present invention is illustrated. This ernbodies a metal punch and stripper having a base I of suitable proportions and strength to support the device when mounted on the shop oor or a table such as found in the ordinary shop or which may be a part'of the base of a press or die unit. At longitudinally opposed ends of the ,l

base I0, upwardly directed brackets I2 and I4 are secured. On the inner, upright face of the bracket |4, which is at the right as viewed in Figs. 1 and 2, a member |6 is anchored, having an annular bore I8. A piston 20, which may be,

formed integral,with a; ram 22, is adapted to register within the opening I8 in the member I6, with the ram 22 extending outwardly thereof through a cap member 24, closing the'end of the bore I8.

At the opposite end of the ram 22, that is to say, the left end as viewed in Figs. 1 and 2, a Y

member 26 on a carriage 30 is secured by bolts keeper bars or gib members 38 bolted to the shoulders 36.

In the upwardly directed leg of the carriage 38,

openings such as indicated at 42 in Fig. 2 ,are

provided which are counterbored in the forward face of the upwardly directed leg to provide shoulders 44. In each of the openings 42, an annular cylinder 46 is press-fitted and a shoulder portion 48 on each cylinder is brought into abutting relationship with the shoulder 44. Each of the cylinders l46 is provided with an annularV blockedopening 50 in which a piston 52 is posi-E tioned for movement in reciprocation. The forward ends of the openings 50 in the cylinders 46 are closed by a head 54 which is bolted to the 30. A plurality of punches 56 are retained by a punch holder 58 secured to the head 54.

A pressure plate 60 is mounted on the head 54 by spacers 62 through which bolts 64 extend and which are threaded into the cylinder head 54.

, The pressure plate 60 has counterbored openings 66 containing shoulders 68 which are in abutting relationship with shoulders on the spacers 62 when the punches 56 are in a retracted position, as illustrated in Fig. 3. The inside diameter of the smaller portion of the counterbored openings y66 is slightly larger than the outside diameter of the spacers 62 to permit the shifting of the pressure plate 60 axially along the spacers as the punches 56 advance through openings 12 in the pressure plate. This permits the punching end of the punches 56 to enter into operative engagement with a piece of work 14, retained in punching position by the pressure plate.

A die block 18 is mounted on the bracket I2 in which a plurality of dies 80 are' positioned having counterbored openings 82 disposed in alignment with the punches 56 which are capable of passing thereinto. Thus, when the punches 56 are brought into operative engagement with the work 14, each punch is forced through the workpiece 14 and the slug pressed therefrom is advanced into the enlarged portion of the opening 82 in each die and thence discharged by way of a mating opening 84 formed in the bracket l2 outwardly thereof.

' The carriage 30 may be advanced to bring the pressure plate 60 and the punches 56 into engagement with the work 'I4 in any manner, so long as it provides for rigidly and positively holding the work 14 during the punching and stripping operations. For the purpose of illustration, the carriage is shown as being actuated by the piston 20 which is hydraulically operated. Fluid lunder pressure is introduced into a port 88, a

passageway 90 and the bore I8, causing the piston 20 and the carriage 30 to advance in the direction of the work 14.

, port |00 at the bottom of the member 26 in communication with the passageway 90.

Thus, as fluid under pressure enters the bore I8 to move the piston 20 outwardly thereof, it simultaneously enters port 96 by the passageways just described, fcrcing the head end of the plunger 92 into contact with the adjacent face of the piston I'pressure plate 60 contacts one side of the work 14 and is forcibly held thereagainst, as illustrated in Fig. 2, by the rods ma due to the action of face of the upwardly directed leg of the carriage the plunger 92 on the piston 52. The continued movement of the carriage 30 thereafter advances the punches 56 and the spacers 62 relative to the pressure plate 60 to perform the punching operation on the work 14. The forward movement of the carriage 30 is interrupted when the punch holders 58 engage the pressure plate 60. As the spacers 62 and punch 56 are moved forwardly relative to the pressure plate 60, the rods |04, the piston 52 and the plunger 82 are retracted in the lcylinders 46. As the punch 56 passes completely through the work 14, the punched-out slug |08 is carried by the forward end of the punch into the enlarged portion of the opening 82 in the die 80 from which it will eventually drop as additional slugs collect and are advanced therein.

At the termination of the punching operation, the ow of pressurized fluid is reversed by a reversing valve (not shown) and the fluid is directed into port I l0, thence through the passageways ||2 and ||4, and through the reduced passageway ||'6 into the bore |8 on the opposite side of the piston 20 to effect movement of the piston and the carriage 30 in a direction away from the lwork 14. A portion of the passageway ||4 is formed in the movable ram 22 which opens into another passageway ||8 and thence to a port 20; The port |20 is connected by a flexible tube to a port |24 communicating with the interior 50 of the cylinder 46. When pressure is applied to the rearward face of the piston 52, the piston is advanced toward the forward end of the cylinder 48, as the piston20'is being retracted, maintaining the work 14 in clamped position.

Thepassageway ||6 is smaller than the passageway ||4 which provides a full flow of fluid and pressure upon the piston 52 before the piston 20 moves. As pressure builds up on the piston 20, the carriage 30 is moved away from the work 14, withdrawing the punch -therefrom as the work is maintained in clamped position. The advancement of the piston 52 and the rod |04 as the piston 20 is retracted holds the pressure plate 60 against the work 14 throughout the retracting and stripping action, after which the passageway ||4 is closed `to fluid as the return of the carraige 30 is continued. As the punch 58 is being retracted, the continued movement of the carriage 30 away from the work 14 causes the spacers 62 to slide in the opening 66 in the pressure plate 60. After the stripping operation, the shoulder 10 engages the shoulder 68 formed in opening 66 and the pressure plate 60 is carried away from the work 14 with the punch and carriage until the piston reaches retracted position. It is to be understood, of course, that when pressurized fluid is admitted to one or the other of the ports 88 or ||0, the fluid in the unpressurized portion of the system is returned to tank (not illustrated). i

In the form of the invention illustrated in Figures 6 and 7, there is shown a punch and stripping unit which is movable on a fixedly mounted ram. A ram member is provided, which may be ,they ram of a press or die unit, fixed to a machinebr other element to rigidly support the movable mechanism. A'pisto |32 on the ram |30 is positioned within a bore |34 of an inner hydraulic cylinder |36`which forms a portion of the movable part of the unit. An outer housing |38 of the unit also serves as a hydraulic cylinder and is provided with an annular opening |40 in which a floating piston 42 is positioned to move slidably on the inner wall of the opening 40 and the outer wall of the inner cylinder |36. The annular opening |40fof the housing |38 and the open end of the bore |34 in the cylinder |36 are closed by a cylinder head |44 having an opening through which the ram |30 extends. The opposite end of the opening |40 in the housing |38 is closed by a cylinder head |46 which abuts the closed end of the cylinder |36 and is secured in position by a plurality of bolts |48.

The housing |38 is mounted upon ways |50 formed on a base |52 which may be part of a base of the supporting element or lof a die unit. On opposed sides of the base |52, shoulders |54 are provided between which the housing |38 may 'Isin .engagement with a shoulder |12 formed on eachbof the nuts |66.

A die |14 is positioned in line with the punch |68, having a central annular opening |16, the

diameter of which is just slightly greater than the diameter of the reduced end portion of the punch. The die |14 is retained in a holder |18 which, in turn, is anchored to a supporting member |80 which may be formed integral with the base |52. Thus, after I positioning a piece of work |82 with one face thereof against the die |14 and the die holder |18, it is possible to punch an opening yin such work when the punch |60 is forced therethrough due to the action of the unit.

To effect movement of the unit on the ram |30, fluid under pressure may be introduced by way of a passageway |84 into the bore |34 of cylinder |86. With the ram |30 xedly mounted, the cylinder |36 is thereby caused to move toward the left, as viewed in Figure 6, moving the housing |38/and the punch |60 toward the Work |82. Simultaneously, fluid on the opposite side of the piston |32 from the previous operation of the unit no longer under pressure must be discharged. However, the discharge of this unpressurized fluid is controlled by a pressure valve (not shown). As a result, fluid on the opposite side of the piston |32 is prevented from rapidly d-ischarging through an annular groove |86 and passageways |88 and |99 in the ram |30. In this manner, pressure is built up on the discharge side of the hydraulic system and the fluid in the opening |40 of housing |38, which entered therein by way of the passageways |90, |86,

groove |86 and a passageway |92 on a precedingr return movement of the housing |38 toward the right, holds the piston |42 against the inner face of the head |46.

A plurality of rods |94 extend between `the piston |42 and the pressure plate |64. As the housing |38 moves toward the left, the pressure plate |64 is brought into contact with the work |82 and exerts a clamping force thereagainst due to the concerted action of the rods |94 and piston |42. When the pressure plate |64 engages the work |82, the movement of that plate is stopped'and thereafter continued movement `of the unit toward the work |82 brings the punch from its retracted position and causes the same to pass through the work. This movement of the punch causes the slidable nut |66 to move into the opening |68 and forces the piston |42 away from the cylinder head |46 against the pressure of the fluid on the discharge side of the system.

As the punch |60 passes through the work |82, a slug |96 is punched out and carried by the forward end of the punch into the opening |16 of the die |14 from which it eventually passes to an-opening |98 in the supporting member |80 and is droppedexteriorly of the apparatus as additional slugs collect and are advanced therein.

After the punching operation is completed, a reversing valve (not shown) causes fluid under pressure to enter passageways and |88 and thence by way of the annular groove |86 to enter the reduced passageway 200 and the passageway |82. The passageway |92 leads to the opening |40 in the housing |38 and is considerably larger than the passageway 200 which leads to the outer face of the piston |32. The full flow of fluid into opening |40 builds 'up pressure against the face of the piston |42 before the housing moves away from the work |82. Thereafter, pressure builds up on the piston |32, to move the housing |38 away from the work |82, withdrawing the punch therefrom as the work is maintained in clamped position. The pressure applied to piston |42 causes it to advance in the opening |40 toward the cylinder head |46 and thereby holds the pressure plate |64 against the work |82 throughout the retracting and stripping of said punch. This movement of the piston |42 also causes the nut |86 to advance in the opening |68 until the shoulder |12 on the nut engages the shoulder |18 formed in the opening |18 at the termination of the retracting movement of the punch |60. Thereafter, the continued movement of the housing |38 away from the work |82 carries the pressure plate |64 and punch |80 away from the work until the housing |38 is fully retracted. During the retraction of the housing |38, the fluid on the forward side of piston |32, no longer under pressure, is discharged through the passageway |84 to a reservoir (not shown).

In Figs. 8, 9 and 10, there is shown another modication oi the present invention for punching openings on opposed side walls of channels or other similarly shaped structures. In this form of the invention, a base 2 0 is provided having a guide plate 2|2 anchored to the upper surface thereof. A carriage 2|4 is slidably mounted on the guide plate 2 I2 to move on machined ways 2|8 on the upper surface thereof between shoulders 2I8 formed on opposed sides of the guide plate 2|2. A pair of overlying keeper bars or gibs 220 is anchored to the shoulders 2|8 to retain the carriage 2|4 on the guide plate 2|2 for slidable movement in a, manner to be later described. At longitudinally opposed ends of the carriage 2 I4, upwardly directed brackets 222 and 224 are secured.

A ram 228 is xedly anchored to the bracket 224 and has a piston 228 adapted to register within a, bore 230 of a movable hydraulic cylinder 232 in such manner that the ram 228 extends through a cap 234, closing one end of the cylinder. Within the hydraulic cylinder 232, a wall 238 separates the bore 230 from another bore 238 in which a piston 240 is positioned. A cap 242 closes the bore 238 and supports one or a. plurality of punches 244 which are threaded into holders 248 which are secured to the cap 242 by a plate 248. A pressure plate 252, having an opening 254 in registry with the punch 244, is also mounted on the cap 242 by' bolts 258 which are threaded into nuts 258 extending through the plate 248 and slidably retained within openings 280 provided therefor in the cap 242. The nuts 258 are provided with an annular shoulder 282 which is'adapted to be brought into abutting relationship with a shoulder 264 formed inthe openings 260 when the plate 252 is in its most forward position.

A channel shaped piece of work 288 is secured in punching position by a Work holder 288 carried by the base 2|0 in position to be engaged by the punch 244. A cooperating die member 210 vis carried by the work holder 288, having an opening 212 for receiving the punch 244 at the termination of a punching operation.

The bracket 222 on the rleft-hand end ofthe carriage 2 4, as viewed in the figures, is positioned thereon by a key 214 and bolts 215. The bracket is provided with a cylinder bore 218 containing a piston 218 and enclosed by a cap 280 which is bolted thereto. One or a plurality of punches 282 are mounted on the cap 280 when threaded in the holders 284 which are secured to the cap 280 by a plate 288. A pressure plate 288, having ings 288 when the pressure plate is in its forward position.

During operation, the punch 282 is adapted to register with a die 302 retained in the adjacent tace of the work holder 288 and enters the opening 304 provided therefor in the die 302 at the termination of the punching operation.

Because the ram 228 is ilxedly held by the bracket 224 of the carriage 2|4, the hydraulic cylinder 232 is mounted to be slidably shifted on y machined ways 3 |0 provided on the upper surface of the carriage 2|4 between the shoulders 3|2 at opposite sides of the carriage. The cylinder 232 is maintained in its position on the ways 3|0 by overlying keeper bars or gibs 3 |4 which are bolted to the shoulders 3 I2.

In operation, uid under pressure is delivered from any convenient source by way of line 3|8 simultaneously to ports 320 and 322. The port 320 delivers the fluid by way of a passageway 324 through the ram 228 into the bore 238 of the hydraulic cylinder 232 to eiect movement of that cylinder toward the left, as viewed in Figs. 8 and 9. At the same time, entry of pressurized iluid into the bore 230 acts upon a plunger 328 which is slidably mounted in a collar 328 positioned in the separating wall 236 of the cylinder 232, causing the plunger 328 to move into engagement with the piston 240.

A rod or rods 330 extend between the piston 240 and the pressure plate 252 so that when the piston 232 moves toward the workpiece 288, the pressure plate 252 is maintained in its outermost position while the punch 248 remains in fully retracted position. At or about the same instant the plunger 328 is moved into contact with the piston 240, introduction oi' pressurized fluid into the port 322 causes a. plunger 333 to move to contact the piston 218. The plunger 333 is slidably retained by a collar 334 in the outer wall of the bracket 222 and the plunger 333 moves slidably therein to contact the piston 218. Similar to the previously described rod 330, a rod or rods 338 extend between the piston 218 and the pressure plate 288 to effect clamping of the work 288 on the side opposite pressure plate 252.

Continued movement of the hydraulic cylinder 232 toward the workpiece 288 results in bringing the pressure plate 252 into contact with one side member of the work 288, stopping the movement of the pressure plate 252 and causes the same to exert an initial holding pressure on that side of the work 288.

When the movement of the pressure plate 252 is thus stopped, movement of the cylinder 232 toan opening 290 in registry with the punches 282,

ing through the plate 288. The nuts 294 are slidf ably disposed within counterbored openinss 288 ward the work 288 is stopped and the piston 228 moves the ram 226 outwardly of the bore 230. Movement of the ram 228 in this manner brings about shifting of the rcarriage 2 I4 toward the right, as viewed in the figures, against the action of springs 338 and'340. As thecarriage 2|4 thus moves, the pressure plate 288 is` brought into initial holding engagement with the left-hand side of the work 228 due to the action of rod 338 on piston 218.

With the springs 338 and 340 compressed in this manner, continued input of pressurized iiuid into bore 230 retracts the rods 330 and 338 and the pistons 240 and 218 into their respective bores as the punches 244 and 282 move from retracted p0- sitions into contact with opposite sides of work 288 and forces the punches through their respecltive sides of the work 266. The punches 244 and 282 shear slugs from the work 266 which eventually discharge by way of openings 212 and 304 spectively, to cause such pistons to exert a force on the rods 330 and 336 for holding the pressure plates 252 and 288 against opposite sides of the workpiece 266 as the punches 244 and 282 are retracted. The iluid entering port 346 and thence passageway 352 to the bore 230 acts upon the pisl ton 232 to effect the return of the cylinder 232 away from the work 266 permitting the springs 340 and 342 to move the bracket 224 away from the work 266. This return movement of the cylinder 232 and the brackets 224 moves the pressure plates 252 and 268 away from the work 266 so that the same may be removed and a new piece substituted therefor.

While the cylinder 232 and the bracket 224 are returned in this fashion, iluid in the unpressurized portions of the device is returned by way of the previously mentioned passageways and ports 324, 322 and 320 into line 3I8 for return to a reservoir (not shown).

In Figs. ll and 12, still another form of the invention is illustrated. A base 364 has a guide plate 366 mounted on its upper surface on which a carriage 368 is mounted to move slidably upon machined Ways 310 disposed between shoulders g 312 formed thereon. Overlying keeper bars 314,

which are bolted to the shoulders 312 of the guide plate 366, maintain the carriage 364 on the guide plate 366.

Similarly, a hydraulic cylinder 316 is slidably mounted upon machined ways 318 formed on the upper surface of the carriage 368. The hydraulic cylinder 316 is positioned between shoulders 380 formed on opposed sides vof the upper portion of the carriage 368 and overlying keeper bars orgibs 382 are bolted to the shoulders 380 to secure the cylinder 316 thereon.

Brackets 384 and 386 are mounted at opposed longitudinal ends of the carriage 368. A ram 368 is rigidly fixed to the bracket 386 and is provided at its inner end with a piston 390 which is positioned within a bore 392 in the hydraulic cylinder 316 in such manner that the ram 388 extends through a cap 394 which closes the bore 392. In the inner or forward end of the cylinder 316, there is formed another bore 396 in which a pist0n 398 is positioned to be shifted therein in a manner to be later described. The bore 396 is closed by a cap 400 which has a punch 402 secured thereto by a plate 404. A pressure plate 406 is also mounted on the cap 400 in such manner that the pressure plate may move relative to the punch 402 to effect retraction of that punch and the means for thus mounting the pressure plate 406 (not shown) may be identical to those described in the previous forms of the invention A work holder408 is secured to the base 364 upon which a piece of channel-shaped work 4| 0 may be mounted in such manner that one wall thereof is in adjacent relationship-to the pressure plate 406. In the side of the holder 408 adjacent to the pressure plate 406, there is provided a die 4t2 having an openingcentrally thereofv whichis axially aligned with the longitudinal axis of the punch 402 into which the punch may extend.

On the bracket 384, a die supporting plate 4|4 is mounted in adjacent relationship to the opposite side of the work 4|0. A die 4I6 is positioned in the plate 4I4 having an opening 4|8 centrally thereof in 'aligned relation with the opening in the previously mentioned die 4|2. As the punch 402 moves through the work 4|0, the end of the punch passes through each wall of the workpiece 4I0 and removes slugs of metal therefrom which are discharged into an opening 420 which is provided in the bracket 384.

In operation, iluid under pressure from any convenient source is introduced by way of a line 422 into a port 424 and thence by way of a passageway 426, formed in the ram 3 88, into the bore 392 of the hydraulic cylinder 316. When this occurs, the hydraulic cylinder 316 moves in a direction toward the work M0, carrying with it the pressure plate 406. The introduction of pressurized hydraulic fluid into the bore 392 causes a plunger 428, which is slidably .mounted in a collar 430 carried by a separating wall 432 between the bores 392 and 396, to move so that the head of the plunger 428 contacts the piston 398.

A rod 434 extends between the piston 398 and the pressure plate 406, and as the latter is brought into engagement with a side wall of the workpiece 4I0, force is exerted on the pressure plate due to the action of piston 398 on the rod 434 to initially hold the Work 4|0 in punching position. When the pressure plate 406 contacts the side of the workpiece 4|0, the movement of the pressure plate toward the workpiece 4|0 is stopped, as is the movement of the hydraulic cylinder 316.

Continued input of iluid under pressure into cylinder 316 causes the piston 390 to move the ram 388 in a direction away from the work 4I0,

40 effecting movement of the carriage 368 against the action of springs 436 and 438, to move the bracket 384 and the die supporting plate 4|4 toward the work 4|0 until the plate contacts the opposite side of the work 4l0. As soon as the work 4l0 is clamped between the plates 406 and 4|4, movement of the carriage 368 is stopped, and thereafter the uid pressure effects further movement of the hydraulic cylinder 316 toward the work 4I0. The rod or rods 434, along with the piston 398. retract into the bore 396 as the punch 402 advances from its retracted position and passes rst through the wall of the work 4|0 adjacent thereto and through the holder 408 and thus through Athe opposite wall of the work 4|0 to punch openings in each side wall of the work.

After the openings have been punched in each side Wall of the work 4l0, the direction of flow ofY the nnpressurized fluid is reversed by` a re- Y versing valve (not shown) and fluid under pressure is simultaneously introduced by way of a line 440 into 'ports 442 and 444. The iiuid passing through port 444 is introduced into the bore 396 to act against the outer face of the piston 398, for holding the pressure plate 406 against the work 4|0 during the movement of the punch 402 into retracted position. The plate 4|4 is held against the work 4I0 during the retracting movement of the cylinder and the punch 402.

passagewayv446 into the bore 392 to exert a pressure between the piston 390 and cap 394. The cylinder 316 moves away from the work 4I0 until the punch 402 is brought into its retracted position. Further movement of the cylinder 316 to the right releases the plates aus and 4 l 4 from con- The fluid introduced into port 442 travels by way of a 11 tact with the work through the action of the springs 436 and 438. The work 4I0 may then be removed from the holder 408 and a new piece substituted therefor.

Referring to Figs. 13 and 14, the form of the invention therein illustrated embodies a carriage 450 on which a housing 452 is secured by suitable means, herein illustrated as by a key 454 and bolts 455. The carriage 450 is mounted upon suitable ways to permit the carriage and housing 452 to reciprocate thereon. The housing con, tains a cylindrical opening 456 in which a piston 458 extends from a piston rod 460, the free end of which rod is attached to a mounting adapter 462 which may be secured to a press, standard or other anchoring means. The housing forwardly of the cylinder 4'56 is provided with a wall 464 containing a collar 466 in which a reciprocal plunger 468 is sealed. The housing also contains a pair of cylindrical openings 410 in which plungers 412 are sealed for reciprocating movement. A collar 414 about the piston rod 460 is sealed to the end of the housing and provided on its outer surface with an annular channel 416 communicating with passageways 418 in communicationY with the cylindrical openings 410. The piston rod 460 has an annular channel 480 on its exterior surface which communicates through a passageway 482 with a longitudinally extending passageway 484. A passageway 486 extends through the wall of the collar 414 from the annular passageway 416 provided therein. The passageway 486 communicates with a passageway 488 of reduced area which supplies fluid to a shoulder 490 on the piston 458 when the punches are to be retracted. A movable plate 492 is provided in a recess 494 in the forward end of the housing 452 in contact with the plungers 468 and 412. Punches 496 are carried by the housing forwardly of the plate 492, which plate supports a pressure plate 498 which moves with the plate 492 through the rods 500 in contact therewith. The detail of this structure is not illustrated as it follows the same construction as `that of the devices hereinbefore illustrated and described.

Fluid is admitted into a passageway 502 in the piston rod 460 to provide a pressure within the cylindrical opening 456 which acts upon the plunger 468 to move the plate 492, rods 500 and pressure plate 498 away from the housing 452. Thereafter, the housing 452 advances on the piston 458 to move the punches 496 toward and through the work as the plate 492 and plungers 468 and 412 retract within the housing as fluid in the cylindrical opening 410 is conducted to the tank (not illustrated).

After the punching operation., the fluid is reversed and pressure is applied through the port- 484 into the passageway 418 which applies pressure to the plungers 412 to provide an outward force to the plate 492, rods 500 and the pressure plate 498 to hold the work while pressure builds up between the collar 414 and shoulder 490 to produce the retraction of the housing 452 and therefore of the punches 496. After the punches are withdrawn and the pressure plate 498 has reached its outward position, the further movement of the housing 452 moves the pressure plate from engagement with the Work which may then be removed.

Referring to Figs. 15 and 16, a still further form of the invention is illustrated. that wherein the carriage 450 of the housing 452 is mounted in ways 506 and the piston rod 460 is anchored in a standard 508 which projects upwardly from a.

table 5I0 having a standard 5l2 on the opposite end. The table 5I0 operates'in ways 5l4 on a bed 5I6 which has a standard 518 on the end thereof adjacent to the standard 508. The table has a screw 520 threaded therein which is movable through an aperture in the standard 518. The head of the screw engages the standard 5H for limiting its movement to the left, as viewed in the figure. A second adjustable screw 522 is carried by the standard for limiting the movement of the carriage 5l0 to the right.

The carriage is provided with a cylindrical opening 524, having a piston 526 therein which engages the end of a plunger 528 extending through a collar 530 into engagement with the standard 5|8. With this construction, the table 5|01 is shiftable on the base 5|6 so that a die 532, supported by the standard 5I2, may adjust itself over a fiange on the workpiece after the workpiece has been disposed between the die and the punch 496.

Upon the application of fluid pressure into the cylindricall opening 456, the movement vof the housing 452 toward the work first causes the pressure plate 498 to engage the work, after which the movement of the housing 452 ceases and the piston 458 moves outward of the cylindrical opening 456 to thereby move the carriage 5I0 to the right, as viewed in the figure, and advance the die 532 into engagement with the work. Continued application of fluid into the cylindrical opening 456 again advances the housing 452 to the left to thereby move the punches 496 through the work. Upon the reversal of the ow of fluid from the aperture 502 to the aperture 484 in the piston rod, fluid is also directed through the conduit'534 to the cylinder 524 to thereby advance the table 5l0 to the left after the punch 496 has been withdrawn from the work to clear the die 1532 from the flange of the work so that the work may be removed.

Referring to Figs. 18 and 19, a similar device as that illustrated in Figs. 15 and 16 is shown, which is of very narrow construction. In this arrangement, a housing 536 is provided with a cylindrical aperture 456 containing the piston 458 having the piston rod 460 provided with the passageways 502 and 484. The piston rod is secured to the carriage 508 which is shiftable on the base 538. The housing 536 is shiftable in ways 540 on the carriage 508. The die 532 is supported on the standard 5I2 on the table 5l0 and the pressure plate 498 is supported on the guide elements 542 secured to the die supporting plate 544 attached to the forward end of the housing 536. A cylindrical opening 546 is provided forwardly of the cylindrical opening 456 in the housing 536, the wall 548 therebetween having a sleeve bushing 550 extending therethrough in which a plunger 552 reciprocates. The plunger abuis a piston 554 which is sealed to the Wall of the cylindrical opening 546 and which engages a rod or rods 556 which abut the pressure plate 498. A passageway 558 leads from the rear end of the cylindrical opening 546 to an annular aperture 560 provided about the collar 414. With this arrangement, the application of fluid to the side of the piston 554 adjacent to the Wall 548 occurs in the same manner as that of the structure of Figs. 13 and 14, hereinabove specifically described, upon the reversal of flow of fluid. This produces the Withdrawal of the punches from the work. the subsequent withdrawal of the pressure plate and the shifting of the supporting table to have the die and pressure plate free of the work. By

y therefor by mounting the housing in a vertical instead of a horizontal plane to thereby maintain the narrow construction and provide a support for a plurality of punches in a substantially vertical plane within the width of the device.

' In the constructions herein illustrated, the application of fluid to the secondary cylinders for advancing the pistons therein and forcing the pressure plates against the work, produces a reactive force which moves the housings or main piston sufficiently to withdraw the punch from the work. After the movement of the secondary pistons has terminated, the further application of uid into the main cylinder continues the retractive movement of the housing until the main piston has completed its stroke relative to the cylinder, and the housing or piston has returned to its initial position.`

Referring more specifically to Figs. 13 and 14. the fluid for retracting the housng enters the passageway 484, the annular passageway 482,the passageway 418, to the cylindrical openings 410 to force the plate 482 forwardly to thereby pro-v duce the retraction of the housing over the plate and the withdrawal of the punches 496 from the.

work.

It will be noted in Figs. 13 and 14 that the plate 492 and pistons 412 are in the most forward position, while the housing 452 is also in the most forward position. This condition would occur when the advancement of the elements takes place without the pressure plate 498 contacting the work. The fluid from the passageway 484 would pass through the passageway 488 to produce the retractive movement of the housing 452 until the annular passageway 482 advances beyond the end of the sleeve *414, at which time the introduction of the larger volume of fluid into the area of the shoulder 488 would produce the rapid return of the housing. The aperture 488 is small compared to the aperture 486, in

"eration The use of the relief valve or the plunger the order of approximately one to ten, to assure .the housing 452, the passageway 484 may be extended, as at 582, and connected by a passageway 584 in communication with the shoulder 488 so as to be available to admit or bleed off fluid from the shoulder area when the annular passageway 482 has cut 0K the return supply of fluid from the passageway 488 to the passageway 484.

It will be noted that in the above mentioned patent, a relief valve is employed for relieving the pressure of fluid on the pressure plate as the housing advances to produce the operation on the work. 'I'his pressure valve is elimnated in the present construction through the differential areas provided between thefplungers 82, 82S, 383, 428, 488 and 552 and the cylinder in which the end projects. With this arrangement, the initial pressure in the` cylinders forces the plunger forwardly to advance the pressure plate to its advanced position as the housing advances the pressure plate into contact with the work.. The further application of pressurized fluid to the cylinder continues the movement of the housing while permitting the plunger to retract within projecting within the main cylinderl provides a predetermined hold-down pressure for the work before and during the punching operation.

'Ihe structure of the present invention readily lends itself to the construction of a variety of types of punching machines. Any number of the devices may be assembled on a bed in predetermined relation to the work which is clamped in position therein. 'I'he devices are operated serially 0r simultaneously to apply pressure to the pressure plate which is moved with the punches into engagement with the work. This is usually accomplished by fluid supplied in large volume and at low pressure in the order of 500 to 1000 p. s. i. Thereafter, fluid is supplied in low volume and at high pressure in the order of 5000 to 10,000 p. s. i. to force the` punch or punches through the work. The withdrawal of the punches and theA`v retraction of the devices to their initial positions are accomplished by the fluid supplied at low pressure.

It is to be understood that in any of the constructions herein illustrated the cylinder may move on a fixed piston or be maintained stationary while the piston is free to move. It is further to be understood that fluid can be directed into the cylinders of the punch -retracting pistons through passageways in the main cylinder wall from the piston rod, as'shown in Figs. 3 and 13, thereby eliminating the necessity of employing flexible conduits for conducting fluid thereto as illustrated.

What is claimed is:

1. In a device for operating on a piece of work, a cylinder and piston one of which is anchored in xed position, a second cylinder and piston, a pressure plate associated with said second cylinder and piston, a plunger in fluid communication with said first cylinder and in engagement with said second piston for clamping the work during the punching operation, and a punch carried by said ilrst cylinder and piston and advanced through the work thereby after the pressure plate engages and holds the work, said punch being retractable from the work by the operation of the second cylinder and piston while forcing the pressure plate toward the work when pressure is relieved from sa-id rst cylinder and piston. v

2. In a device for operating on a piece of work, a cylinder and piston one of which is anchored in fixed position, a pressure plate associated with said cylinder and piston, a plunger, a second cylinder and piston engaging the pressure plate and movable by said plunge, and means for supporting a punch by said rst cylinder and piston, said plunger being of smaller diameter than the flrst piston so that when fluid is delivered simultaneously to the plunger and piston the pressure plate and second piston will move to advanced position and be moved by the cylinder and piston to engage and hold the work as the punch is advanced therethrough as the plunger retracts against the pressure applied thereto.

3. In a device for punching holes in a workpiece, a first cylinder and piston having a punch associated therewith for performing a punching operation, a plunger extending from said cylinder for initially applying pressure on the workpiece and retractable against the pressure therein during the punching operation, and a second cylinder and piston of substantially greater diameter, than said plunger for retracting the to the cylinder for initially applying pressure on the workpiece and retractable in the cylinder against the pressure therein during the punching operation, and a second cylinder and piston for retracting the punch from the work as the work is held thereby, the second cylinder, piston and punch being retractable from the work by the operation of the rst cylinder and piston thereafter.

5. In a device for holding a workpiece for performing a punching operation thereon including, in combination, a cylinder and piston one of which is secured in fixed position, a pressure plate.

and aplunger engaging said pressure plate and projecting into said cylinder to be independently actuated by the fluid therein, said plunger being of smaller diameter than the diameter of the cylinder for actuating said pressure plate away from said cylinder independently of the piston when fluid under pressure is directed thereinto to relatively advance said cylinder and piston in the direction said pressure plate has advanced.

6. In a device for holdinga workpiece while performing an operation thereon including, in combination, a movable cylinder, a piston in said cylinder, a pressure plate supported for limited movement on said cylinder, a plunger engaging said pressure plate and projecting into said cylinder, said plunger being of a diameter substantially less than the diameter of the cylinder, and a second cylinder and piston associated with said first cylinder disposed in position tol apply pressure to said pressure plate when pressure is reversed in said rst cylinder, the reaction to which moves the rst cylinder away from the pressure plate.

'7. In a device for holding the work and performing a punching operation thereon including, in combination, a xed cylinder, a movable piston in said cylinder, a slide moved by said piston, a pressure plate mounted on said slide for limited movement, means for supporting a punch on said slide,and a second cylinder and piston carried by said slide having operative engagement with said pressure plate and movable by the first said piston into engagement with the work which thereafter remains stationary while the punching pration occurs.

8. In a device for holding the work and performing a punching operation thereon including, in combination, a fixed cylinder, a movable piston in said cylinder, a slide movable by said piston, a pressure plate mounted on said slide for limited movement, means for supporting a punch on said slide, and a second cylinder and piston carried by said slide having operative engagement with said pressure plate and movable by the first said piston into engagement with the work which thereafter remains stationary while the punching operation occurs, said second cylinder and piston applying a holding force to the pressure plate and work after the pressure is reversed in said first cylinder and applied to said second cylinder, the reaction to which retracts the slide an amount to withdraw the punch from the work.

9. In a device for holding the work and performing a punching operation thereon including, in combination, a cylinder. a movable piston in said cylinder, a slide movable by said piston, a pressure plate mounted on said slide for limited movement, means for supporting a punch on said slide, a plunger on said slide for advancing the pressure plate therefrom when fluid directed into the cylinder is conducted thereto, and a second cylinder and piston carried by said slide having operative engagement with said pressure plate, said pressure plate being adapted to be moved by the rst said cylinder into engagement with the work which thereafter remains stationary while the punching operation occurs and the plunger retracts, said second cylinder and piston applying a holding force to the pressure plate and work after the pressure is reversed on said rst cylinder, the reaction to which retracts the rst cylinder an amount to withdraw the punch from the work, said first cylinder thereafter returning the slide to its initial position.

10. In a device for securing the work while punching an aperture therethrough, a cylinder and piston and means by which one portion thereof is secured in fixed position, a slide operated by the movable portion of said cylinder and piston, a second cylinder and piston in said slide, a plunger carried by the slide, a pressure plate supported by the slide and engaged by said plunger, a conduit conducting fluid to said first cylinder and said plunger, and a punch carried by the slide and projectable beyond the pressure plate whereby the relative movement between the rst said cylinder and pistonv advances the slide to move the pressure plate into engagement with the work through which the punch is thereafter forced, the punches being retracted from the work thereafterby the operation of the second cylinder and piston when applying a holding force to the plate after the pressure is relieved from said first cylinder.

11. In combination with a device for holding the work and performing a punching operation thereon, a fixed cylinder, a piston movable therein, a slide movable by said piston, means for supporting a punch on said slide, a pair of spaced cylinders and pistons provided in said movable slide, a plunger on said slide of a diameter less than the diameter of the cylinder, a conduit conducting fluid to said cylinder and said plunger, and a pressure plate carried by said slide for limited movement thereon engageable by said plunger and said spaced pistons for applying a forward movement thereto whereby the movement of the slide by said first piston applies a pressure to the plunger and advances the pressure plate into engagement with the work through which the punches are thereafter forced, and after pressure is relieved from the first cylinder and piston, the pressure on the spaced pistons applying a forward pressure on the pressure plate and a retractive force on the slide for withdrawing the punches from the work.

12. In a device for holding and'punching apertures in workpieces, a reciprocable housing having a central cylinder containing a xed piston, an annular cylinder and piston disposed around said flrst cylinder and piston, a pressure plate carried by said housing for limited movement under the control of said annular piston, and means on said housing for supporting the punch whereby the advancement of the housing on the fixed piston moves the pressure plate into engagement with the work and the punch through the work thereafter for performing the punching operation.

13. In a device for holding and punching aperan annular cylinder and piston disposed around said first cylinder and piston. a pressure plate carried by said housing for limited movement under the control of said annular piston. and means on said housing for supporting the punch whereby the advancement of the housing on the fixed,

piston moves the pressure plate into engagement with the work and the punch through the work thereafter for performing the punching operainder and piston producing the retraction of thev punch and the application of pressure to the pressure plate. K

14. In combination with a device for holding the work and performing a punching operation thereon including, in combination, a table, a cylinder and piston one element of which is secured to one end of the table, a pair of cylinders and pistons one xed to the opposite end of the table from the first said cylinder and piston, the other of which is shiftable relative to the table by the first said cylinder and piston, a pressure plate carried by each of said pairs of cylinders and pistons for limited movement and operated toward each other with a predetermined force which is less than that applied by said first cylinder and piston to move the pressure plates into engagement with opposite sides of the Work as the table is shifted on the base thereby, and a punch carried by each of said pairs of cylinders and pistons, the continued operation of the first cylinder and piston producing further relative movement of the table and the advancement of the punches through the work, the reversal of fluid thereafter in the first cylinder and piston and the application of greater pressure to the pressure plate by the second cylinder and piston securely holding the work while the punches are retracted therefrom.

15. In combination with a device for holding the work and performing a punching operation thereon including, in combination, a table, a cylinder and piston one element of which is secured to one end of the table, a pair of cylinders and pistons one fixed to the opposite end of the table from the rst said cylinder and piston, the other of which is shiftable relative to the table by the first said cylinder and piston, a pressure plate carried by each of said pairs of cylinders and pistons for limited movement .and operated toward each other with a predetermined force which is less than that applied by said first cylinder and piston to move the pressure plates into engagement with opposite sides of the work as the table is shifted on the base thereby, a punch carried by each of said pairs of cylinders and pistons, the continued operation of the rst cylinder and piston producing further relative movement of the table and the advancement of the punches through the work, the reversal of fluid thereafter in the first cylinder and piston and the application of greater pressure to the pressure plate by the second cylinder and piston securely holding the work while the punches are retracted therefrom, and means for positioning said table on the base.

16. In a device for punching holes in the spaced 18 the opposite end ci thecarriage from that of the first cylinder and piston, the other Voi' which is mounted for movement by said rst cylinder and piston relative to said carriage, pressure plates supported by said pair of cylinders for limited movement outwardly thereof toward each other. and means on said pair of cylinders for supporting a punch wherebyrthe application of pressure to the first cylinder and piston advances the pressure plates into engagement with the spaced walls of the channel element through the shifting of the carriage which is further shifted thereafter as the punches are advanced beyond the pressure plate through the spaced walls of the element.

17. In a device for punching holes in the spaced walls of a channel element which includes, in combination, a shiftable carriage, a fixed support for the work, a cylinder and piston one of which is secured to one end of the carriage, a pair of cylinders and pistons one of which-is mounted on the opposite end of the carriage from that of the first cylinder and piston, the other of which is mounted for movement by said first cylinder and piston relative to said carriage, pressure plates supported by said pair of cylinders for limited movement outwardly ,thereof toward each other, and means on said pair of cylinders for supporting a punch whereby the application of pressure walls of a channel element which includes, in l to the first cylinder and piston advances the pressure plates into engagement with the spaced walls of the channel element through the shifting of' the carriage which is further shifted thereafter as the punches are advanced beyond the pressure plates through the spaced walls of the element, the application of pressure to the pair of pistons upon the reversal of the fluid in the first said cylinder and piston procuring the clamping of the pressure plates against the work and the retraction of the punches from the walls of the element.

18. In a device for punching holes in the spaced walls of a channel element which includes, in combination, a shiftable carriage, a fixed support for the work, a cylinder and piston one of which is secured to one end of the carriage, a pair of cylinders and pistons one of which is mounted on the opposite end of the carriage from that of the first cylinder and piston, the other of which is mounted for movement by said first cylinder and piston relative to said carriage, pressure plates supported by said pair of cylinders for limited movement outwardly thereof toward each other, and means on said pair of cylinders for supporting a punch whereby the application of pressure to the first cylinder "and piston advances the pressure plates into engagement with the spaced walls of the channel element through the shifting of the carriage which is further shifted thereafter as the punches are advanced beyond the pressure plates through the spaced walls of the element, the application of pressure to the pair of pistons upon the reversal of the, fluid in the first said cylinder and piston procuring the clamping of the pressure plates against the work and the retraction of the punchesV from the walls of the element, the punches and pressure plate being further removed away from each other to their initial relative positions by the actuation of the first cylinder and piston.

19. In a device for punching holes in the spaced walls of a channel element which includes, in combination, a shiftable carriage, a fixed support for the work. a cylinder and piston one of which is secured to one end of the carriage, a pair of cylinders and pistons one of which is mounted on 'Il on the opposite end of the carriage from that of 19 the iii-st cylinder and piston, the other of which is mounted for movement by said iirst cylinder and piston relative to said carriage. pressure plates supported by said pair of cylinders ior limited movement outwardly thereof toward each other, means on said pair of cylinders for supporting a punch whereby the application of pressure to the ilrst cylinder and piston advances the pressure plates into engagement with the spaced walls of the channel element through the shitting or the carriage which is further shifted thereafter as `the punches are advanced beyond the pressure I work holder.

20. In a device for holding and performing a work operation on a workpiece, a main cylinder and piston, a pressure plate, a second cylinder and piston engaging and moving said pressure plate, and a plunger in said main cylinder of less diameter than said main cylinder for applying initial pressure to said pressure plate when pressure is applied to said main cylinder and piston, said second cylinder and piston being of greater diameter than said plunger for applying a forward holding force to said pressure plate sumcient to produce the relative retraction of said ilrst cylinder and piston when the initial pressure is released therefrom.

21. In a device for clamping and holding a workpiece, a housing containing a ilrst cylinder and piston, a pressure plate mounted on said housing for limited movement, a plunger projecting in said Ycylinder contacting said plate and i the first cylinder and piston return the housing having a diameter substantially less than the cli- 1 ameter of the cylinder, and a pair of spaced cylinders and pistons in said housing disposed to have the pistons contactl said pressure plate whereby the plate is held in advanced position by the operation of the plunger when fluid is initially applied to said ilrst cylinder and piston. to ad- Vance the pressure plate and housing to have the work engaged by the pressure plate which retracts toward the housing as the housing cony tinues to advance toward the workpiece.

22. In a device for clamping and holding a work piece, a housing containing a first cylinder and piston, a pressure plate mounted on said housing for limited movement, a plunger projecting in said cylinder contacting said plate and having a diameter substantially less than the diameter of the cylinder, and aY pair of spaced cylinders and pistons in said housing disposed to have the pistons contact said pressure plate whereby the plate is held in advanced position by the operation of the plunger when fluid is initially applied to said rst cylinder and piston to advance the pressure plate and housing to have the work engaged by the pressure plate which retracts toward the housing as the housing continues to advance toward the workpiece, the reversal of pressure on the rst cylinder and piston and the application of pressure to the pair of cylinders and pistons causing the pair of pistons to apply a holding pressure to the pressure plate, the reactive force of which moves to its initial position when iluid is reversed therein. Y

23. In a device for clamping and holding a workpiece, a housing containing a first cylinder and piston, a pressure plate mounted on said housing for limited movement, a plunger projecting in said cylinder contacting said plate and having a diameter substantially less than the diameter of the cylinder, a pair of spaced cylin ders and pistons in said housing disposed to have the pistons contact said pressure plate whereby the plate is held in advanced position by the operation of the plunger when uid is initially applied to said lrst cylinder and piston to advance the pressure plate and housing to have the work engaged by the pressure plate which retracts toward the housing as the housing continues to advance toward the workpiece, the reversal of pressure on the first cylinder and piston and the application of pressure to the pair of cylinders and pistons causing the pair of pistons to apply a holding pressure to the pressure plate, the reactive force of which moves the housing away from the work, after which the first cylinder and piston return the housing to its initial position when fluid is reversed therein, a bed, a carriage on said bed to which one end of said main piston is secured,means on the opposite end of the carriage for supporting a work engaging element which is advanced into engagement with the work after thepressure plate is advanced thereagainst by the movement of the first cylinder and piston through the shifting of the carriage, and a cylinder and piston on said carriage by which said carriage is moved to its initial position.

24. In a device for holding the work and performing a punching operation thereon including. in combination, a fixed cylinder, a movable piston within said cylinder, a slide secured to said piston, a second piston and cylinder on said slide a pressure plate carried by said slide in advance of said second piston, rod means connecting said second piston to said .pressure plate, a plunger in said second cylinder on the opposite side thereof from said pressure plate for advancing the piston of said second cylinder and the pressure plate, a conduit connected to said plunger and to said first cylinder from the end thereof opposite to the slide, and a punch carried by said slide operable relative to said pressure plate. A

25. In a device for holding the work and performing a punching operation thereon including, in combination, a xed piston, a cylinder movable over said piston, a second piston and cylinder carried by said first cylinder, a plunger operated by iluid pressure in said rst cylinder and operatively engaging said second piston for advancing it in the second cylinder, a pressure plate carried by said first cylinder forwardly of said second cylinder, rod means interconnecting the second piston and pressure plate, and a punch carried by said first cylinder forwardly of said second cylinder and movable relative to said pressure plate.

26. In a device for holding the work and performing a punching operation thereon including, in combination. a xed piston, a cylinder movable over said piston, a second piston and cylinder carried by said iirst cylinder, a plunger operated by iluid pressure in said rst cylinder and operatively engaging said second piston for advancing it in the second cylinder. a pressure platev carried by said first cylinder forwardly of said second cylinder, rod means interconnecting the second piston and pressure plate, a punch carried by said iirst cylinder forwardly of said second cylinder and movable relative to said pressure plate. a slide to which said iirst piston is fixed, a third cylinder and .piston carried by the opposite end of the slide from that to which the ilrst piston is secured, a second plunger projecting into the third cylinder in contact with the piston thereof, means by which a iiuid pressure is applied to the second plunger when tiuid pressure is applied to the rst cylinder and plunger, a pressure plate carried by said third cylinder. rod means interconnecting the pressure plate to said third piston, and a punch carried by said third cylinder movable relative to said pressure plate.

27. In a device for holding the work and performing a punching operation thereon including, in combination, afiixed piston. a. cylinder movable over said piston, a second piston and cylinder carried by said iirst cylinder, a plunger operated by fluid pressure in said first cylinder and operatively engaging said second piston for advancing it in the second cylinder, a pressure plate carried by said iirst cylinder forwardly of said second cylinder, rod means interconnecting the second piston and pressure plate, a punch car.-

22 ried by said nrst cylinder forwardly of said second cylinder and movable relative to said pressure plate. a slide to which said iirst piston is iixed, a third cylinder and piston carried by the opposite end of the slide from that to which the iirst piston is secured, a second plunger projecting into the third cylinder in contact with the piston thereof, means by which a. iiuid pressure is applied tothe second plunger when iiuid pressure is applied to the first cylinder and plunger, a pressure plate carried by said third cylinder, rod means interconnecting the pressure plate to said third piston, a punch carried by said third cylinder movable relative to said pressure plate, a iixed work support between said pressure plates, and means for centering said slide relative to said work suport.

OTTO MUELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 2,353,488 Mueller July 11, 1944 

